Today's common household incandescent light bulb bases and receiving sockets remain compatible with Thomas Edison's design. Such compatibility is useful, but it prolongs a safety issue that has increased substantially since Mr. Edison's day. As seen in prior art FIG. 1A, the typical Edison bulb 100 includes the bulb 101 and lower section having a threaded base 103 which fastens within an accompanying luminare socket. Prior art FIG. 2 illustrates the bottom view of the Edison or threaded base wherein a contact 105 located at the center of the concentric conductor 107 is used to supply electrical current to filaments (not shown) within the glass envelope. The contact 105 and concentric conductor 107 are insulated from the threaded base 103 using an insulative material 109. The threaded base 103 screws into an accompanying luminare socket (not shown) that is connected to a lamp or other electrical device. The luminare socket typically uses a flat spring bar which makes electrical contact with a corresponding contact 105 on the bottom of the threaded base 103. Luminare socket manufacturers typically apply warning labels or other indicia on the luminare socket with recommendations for the maximum wattage bulb that is to be used with the base. When these recommendations are followed, this limits both the heat generated by the bulb and electrical current used by the device.
Those skilled in the art will recognize that there is no way to assure that these recommendations to consumers will be followed. For example, a 200-watt incandescent bulb is the same size as a 40-watt bulb, but it generates much more heat when illuminated. Excessive heat can deteriorate the insulation both on the electrical wires connecting to the luminare socket and on the supply wires in the junction box above the luminare. This deterioration, typically in the form of brittleness and cracking, can lead to arcing, and a subsequent fire.
Previous inventors have made adjustments to Edison's light bulb base design. U.S. Pat. No. 656,284, which is incorporated by reference herein, teaches the use of bulb tips having various sizes to prevent other bulbs or fuses from being interchanged. U.S. Pat. No. 4,456,322, which is also incorporated by reference herein, discloses lamp wattage limiting devices that use a contact having a predefined geometric configuration to define the bulb wattage that may be used on the luminare socket. U.S. Pat. Nos. 2,519,328; 2,701,868; 2,999,220; 3,131,986; 3,309,646; and 5,401,191, which are all incorporated by reference herein, show various contact and socket base configurations that allow use with multiple filament bulbs.
Consequently, the need exists for a bulb and luminare socket where the maximum wattage of the bulb is controlled by the socket of the luminare. Moreover, any newly designed light bulb bases must be compatible with existing Edison sockets, and existing light bulbs must work in at least some of the newly designed sockets.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.